A mother killed herself and her two daughters early Tuesday morning in an apparent double murder-suicide near Albany, police report.

Angela Mtambu was found with her daughters, Kutenda, 6 and Cara, 11, inside their townhouse at 58 Rockrose Drive in East Greenbush at 1:44 a.m., timesunion.com reported. All three were dying when police broke down the door to the room they were locked in.

Bernard Pamberi, Mtambu's brother, said there was no sign of irregular behavior from Mtambu on Monday, the day before the incident.

"We spent the whole day, yesterday, with the children, and they went to Hoffman Park," Pamberi said on Tuesday. "We went for dinner at Applebee's restaurant. We took them for ice cream at the fun plex."

Pamberi and another brother were awoken by a hissing sound in the early hours of Tuesday morning.

Mtambu had locked the brothers in their bedroom. They managed to escape the room only to find that the door to the room where Mtambu and the girls were sleeping was also locked.

Unable to break the door down, they called the police, who managed to open the door and found Mtambu and the girls in grave condition on the other side, Time Warner Cable News reported.

"When they crashed down the door, there she was, you know, with the children with the plastic bags and the two tanks there," Pamberi told reporters.

Authorities believe natural gas was used to kill the family, according to The Daily Gazette.

The mother and daughters were transported to Albany Medical Center, but pronounced dead at the hospital.

Pamberi believes his sister killed herself and her children because she was wracked with grief over the recent suicide of her son, Mitchell Gwatida, 23, in April. He said Mtambu killed the girls in the same room where Gwatida killed himself.

"She was going through all this grieving. And I just think that triggered all this. She couldn't take it," Pamberi said. He also said that Mtambu was recently released from a mental institution in Pennsylvania, and that social services workers there had made allegations that "the kids were not very safe with her."

East Greenbush police are now trying to track down the father of the two girls, who is their next of kin.